The present invention relates to photographic silver halide color materials and to processes for the formation of photographic color images.
Existing commercial photographic silver halide color materials form dye images by the reaction of oxidized p-phenylenediamine color developers with a color coupler. The color developing solutions employed contain the color developing agent and used developer solutions need to be disposed of safely. Attempts have been made to incorporate p-phenylene-diamine color developing agents into silver halide photographic materials but these have had little success largely due to the pronounced staining produced.
The use of aryl and heterocyclic sulphonhydrazides as color developers in aqueous color developer solutions which form an azo dye on coupling with a color coupler are described in U.S. Pat. No. 2,424,256, and copending British application 9125688.3 respectively.
It is well known in conventional p-phenylenediamine color forming chemistry to release a group from the coupling position (usually called a Coupling Off Group or COG) which has a photographic effect, e.g. development inhibition. By the release of such a compound one color layer can affect the image formation in an adjacent color layer. Such an effect is not available to sulphonhydrazide image forming chemistry as shown by the following scheme: ##STR1##
The leuco dye is essentially colorless and the COG cannot leave to form a dye.
U.S. Pat. No. 4,108,663 describes the use of inhibitor releasing sulphonamido-phenol developers (IRDs) in conventional p-phenylene-diamine color forming chemistry.
European Patent 0 242 685 describes hydrazide compounds that release photographically useful fragments during silver halide development.
The present invention employs compounds which are capable of releasing a development inhibitor in systems where the color developer is a sulphonhydrazide.